Re: [O] About the use of PROPERTY "meta lines"...

[Torsten Wagner]

Hmm...
but this point is really interesting at least worse to write down in the 
manual.
From my understanding a
#+PROPERTY: var bar=2
sets bar globally to 2
somewhere and many lines and headers later
#+PROPERTY: var bar=5
would change this value to 5 for either the rest of the file or until a 
new assignment is given...
in that way a property line would be an tree-independent global variable

in contrast, a property-block is only valid of the given tree (and 
subtrees?).

This brings up the question if there is a need for

#+PROPERTY: const bar=2

which would behave exactly the same like var but issue an error message 
if someone tries to set it again somewhere in the file.

Torsten



On 01/06/2012 04:28 PM, Eric Schulte wrote:
> "Sebastien Vauban"<address@hidden>  writes:
>
> > Hi Eric and all,
> >
> > Eric Schulte wrote:
> > > "Sebastien Vauban"<address@hidden>  writes:
> > >
> > > > #+TITLE:     Properties
> > > > #+AUTHOR:    Seb Vauban
> > > > #+PROPERTY: var  foo=1
> > > > #+PROPERTY: var+ bar=2
> > > >
> > > > * Abstract
> > > >
> > > > IIUC, properties are set in this way:
> > > >
> > > > - on a file basis, before any heading, through the =PROPERTY= keyword,
> > > > - on a subtree basis, through the =PROPERTIES= block.
> > > >
> > > > My comprehension is that the =PROPERTY= keyword may not be used inside "trees",
> > > > and should be ignored if that would happen.
> > >
> > > While it is not normal usage, I think that it is legal for #+PROPERTY:
> > > lines (or #+Option: lines etc...) to appear inside of subtrees.
> >
> > I realize this is not especially a Babel question, but more a Org core
> > question...
> >
> > Thanks for your answer -- which generates a new one, though: what is then the
> > expected *semantics* of such a construct?
> >
> > There are at least 3 different views on such a construct: putting a PROPERTY
> > line inside a subtree...
> >
> > - ... resets some values from that point up to the end of the subtree
> > - ... resets some values from that point up to the end of the buffer
> > - ... defines some values which can have already been by the subtree
>
> I agree this is murky and whatever behavior we want should be clearly
> thought out and documented in the manual.  I would argue that you missed
> another possible semantics, the simple semantics which are currently
> implemented in which a property line *anywhere* in a buffer sets a
> global property.
>
> Cheers,
>
> > Best regards,
> >    Seb
> >
> > > > The following example shows that either:
> > > >
> > > > - I'm wrong to think so,
> > > > - there is a bug.
> > > >
> > > > What is the right assumption here?
> > > >
> > > > * Subtree
> > > >
> > > > Being located in a subtree, the following lines are ill-placed IMHO:
> > > >
> > > > #+PROPERTY: var  foo="Hello
> > > > #+PROPERTY: var+ world"
> > > >
> > > > Though, they're well taken into account:
> > > >
> > > > #+begin_src emacs-lisp
> > > >    foo
> > > > #+end_src
> > > >
> > > > #+results:
> > > > : Hello world
> > > >
> > > > These lines have even wiped the definition of =bar= (because of the use of =var=
> > > > without any =+=):
> > > >
> > > > #+begin_src emacs-lisp
> > > >    (+ foo bar)
> > > > #+end_src
> > > >
> > > > returns the error "Symbol's value as variable is void: bar."